Cavities guide

How a cavity forms

ADA MouthHealthy explains that plaque, a sticky film of bacteria, constantly forms on your teeth. When you eat or drink sugary foods, the bacteria produce acids, and plaque holds those acids against the enamel. Over time the enamel breaks down and a hole can form. Gum recession can expose tooth roots, which are softer and decay more easily, and decay also commonly forms at the edges of old fillings where bacteria collect.

NIDCR describes the same process in stages: early decay, when minerals are lost from the enamel and a white spot may appear; a cavity, when more minerals are lost than the enamel can restore; and advanced decay, when the tooth may become infected and form an abscess.

What cavities look and feel like

Early cavities are hard to see. Cleveland Clinic says they often look like small white, chalky areas that later turn brown or black, and that a single dark spot on one tooth is more likely to be a cavity than a stain spread across several teeth. Early decay usually has no symptoms, which is why many cavities are found at checkups.

As decay advances you may notice sensitivity to sweet, hot or cold foods, toothache, pain when biting, a visible hole or pit, or a bad taste. Our guide on what cavities look like walks through each stage in more detail.

Can a cavity go away on its own?

Only the earliest stage can reverse. NIDCR says that before a cavity forms, enamel can repair itself using minerals from saliva and fluoride from toothpaste, and that a dentist can apply fluoride to reverse early decay. Cleveland Clinic agrees that very early enamel decay may be reversible with fluoride treatment and better oral hygiene.

Once decay has reached the dentin, the softer layer beneath the enamel, Cleveland Clinic says a filling, crown or other restoration is needed. A hole in a tooth does not heal itself, so waiting can turn a simple filling into a larger repair.

How cavities are found and treated

Dentists find cavities with an examination, instruments and X-rays. Cleveland Clinic says a decayed area may feel softer when probed and that X-rays can reveal decay before it is visible. Treatment depends on the stage.

• Early stage: fluoride treatments, or prescription toothpaste or mouthwash.
• A hole in the tooth: a filling made of composite resin, silver amalgam or gold.
• Advanced decay with pain: root canal therapy, sometimes followed by a crown.
• A tooth that cannot be saved: extraction, possibly followed by a bridge or implant.

What happens after a filling

After a filling you usually resume normal activities, but you should wait for the numbness to fade before eating. Composite hardens during the visit, while amalgam is generally advised to be left alone for about 24 hours. Our guides on dental fillings and on eating after a filling cover the details, including normal sensitivity and when to call.

Can untreated cavities spread or be dangerous?

Cleveland Clinic says untreated decay can lead to tooth loss, a painful abscess, and an infection that can spread through the body, and that this is rarely fatal. In rare cases an abscess can reach the bloodstream or brain. That is why facial swelling, fever or pain that spreads to the jaw or face should be treated as urgent rather than waited out.

Decay also does not stay in one tooth by itself, but the bacteria that cause it are present in the mouth, so new cavities can form elsewhere if plaque is not controlled.

Preventing cavities

Prevention advice is consistent between ADA MouthHealthy, NIDCR and Cleveland Clinic.

• Brush at least twice a day with fluoride toothpaste.
• Floss or use an interdental cleaner every day.
• Limit sugary and starchy foods and drinks, and avoid constant snacking.
• Drink fluoridated tap water where available, and ask about a fluoride rinse if your dentist recommends one.
• Ask about dental sealants for the chewing surfaces of back teeth.
• Avoid tobacco, and see your dentist for checkups and cleanings at least twice a year.

Planning for treatment

If you need a filling, ask which material is planned, how many surfaces are involved, and whether any follow-up is expected. Getting these details in writing makes it easier to compare estimates and to understand what the fee covers.

Guides in this topic

Frequently asked questions